A bonded rare-earth permanent magnet is formed by combining a rare-earth permanent magnetic powder with a bonding material and is directly shaped into various permanent magnet devices through injection molding or compression molding according to the requirement of the user. The magnet has advantages of high dimensional accuracy, excellent magnetic uniformity, high corrosion resistance, high yield, and be easily shaped into a complicated device and so on, and it has been widely applied to household appliances, micro-machines, automatic office equipment, instruments and meters, medical devices, automobiles, magnetic machines and other apparatuses and devices.
Currently, bonded rare-earth permanent magnet powder mainly includes NdFeB magnetic powder and nitride rare-earth magnetic powder. In recent years, with the development of electric motor cars, wind power generation and magnetically levitated trains, a higher requirement is put forward to high-performance and high-stability rare-earth permanent magnets. For nitride rare-earth magnetic powder has high magnetic performance and excellent corrosion resistance, it has been used increasingly widely, thus, how to improve the performance of the nitride rare-earth magnet powder to meet application requirements has been the focus of research.
The nitride rare-earth magnet powder is mainly prepared by nitriding rare-earth alloy powder at a certain temperature for a certain time, the rare-earth alloy powder can be prepared by many methods, including a mechanical alloying method and a rapid quenching method, for example, an isotropic SmFeN powder magnetic material for producing a resin bonded magnet is disclosed in both CN1196144C and JP2002057017, the crystal structure of which is TbCu7 type, the powder is prepared by rapidly quenching a molten alloy and directly nitriding the obtained alloy powder in a nitrogen-containing gas.
A nitride rare-earth powder is disclosed in U.S. Pat. No. 5,750,044 which is also obtained through a rapid quenching and a subsequent nitridizing processing, the magnetic powder includes TbCu7 or Th2Zn17 or Th2Ni17 and a soft magnetic phase, wherein the proportion of the soft magnetic phase is 10-60%. The nitride rare-earth powder, although partly improved in magnetic properties, needs to be researched further so as to meet the requirement of customers for a high-quality product and to be further improved in magnetic properties.